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Facts on Selenium
1) Se is the  symbol for selenium

2) A non-metallic element

3) Atomic no. is 34

4) atomic weight 78.96

5) melting point (of gray selenium) 217C

6) boiling point (gray) 684.9C

7) amorphous 4.28 g/cm

8) gray 4.79 g/cm

9) Valence cell contains two, four, or six electrons

10) exists in the oxidation states of -2, +4, and +6

11) Shells are 1s 2s 2p 3s 3p 3d 4s 4p 

12) Selenium exists in several different forms, including amorphous (noncrystalline), which is red when in powder form and black when in vitreous (glassy) form;

13) the red crystalline; and the gray metallic, which is also crystalline are two other forms

14) the metallic form is the most stable under ordinary conditions; the other forms very slowly convert to the metallic form at room temperature.

15) Has similar chemical and physical properties to sulfur and tellurium

16) Byproduct of electrolytic copper refining

17) Used in rectifiers ( A device, such as a diode, that converts alternating current to direct current) as a semi-conductor

18)  Used in xerography  due to  the electrical conductivity of metallic selenium which increases when light strikes it and converts the light directly into electricity

19) Its photovoltaic and photoconductive actions make it useful in photocells, photographic exposure meters, and solar cells

20) Also used to make red enamels for ceramics and steel ware, as well as for the vulcanization

21) Used in  rubber to increase resistance to abrasion
Selenium is utlized for electricity conduction due to its wide capacity for light absorption.
Selenium is used in xerox machines as well, as it converts the light absorption directly into electricity.
Copyright RDB 2001